Soil for Marijuana Growing Success, Part 2

Managing the use of soil for marijuana growing is challenging but we’re giving you the info you need so you get it right.

In our first article in this series, we gave you valuable information about choosing a brand of soil for marijuana growing, examining soil before you buy it, and adding perlite.

Today we’re talking first about filling pots with soil, and watering soil after the initial fill.

One big mistake cannabis growers make is to pack their soil for marijuana growing too tight or too loose.

If the soil isn’t well-aerated, packing it too tight creates lots of problems that can suffocate or drown roots.

If the soil is packed too loose, it settles during watering so your marijuana plant sinks down, sometimes several inches, and some soil might run out of the bottom of the pot during watering.

The trick is to fill the pot or grow bag to the top, GENTLY press the soil down and add more, then to lift it up and firmly knock it against a flat flooring surface several times to settle the soil.

You may find that the soil settles in and creates pockets, so you have to add more.

What you don’t want to do add too much soil or push the soil into the pot so hard that it compacts it and you lose aeration spacing.

Most people will have their transplant-ready clones or seedlings in tiny rockwool cubes, tiny peat pots, or root shooters.

In some cases, growers might have started their seeds in peat pots that are 2-3 inches in diameter and 2-3 inches tall.

Some people recommend you water your soil before you transplant into it.

I used to do that but now I carefully measure my transplant root spatial needs, excavate the appropriate space in the soil, pack in the space so the transplant is firmly in place, and then I gently water.

Watering is one of the most misunderstood and problematic things marijuana growers do, and it’s almost always overwatering.

My strategy for avoiding overwatering is to weigh my pots after I’ve filled them with new, un-watered soil.

When I water the pot, I want to see its weight increase by 20-35%, depending on growing conditions such as temperature, humidity, growth phase, etc.

If you use the same size pots and the same type of soil for several seasons, you’ll soon be so experienced that you can use weight to know when the soil is dry without even having to put the pots on a scale.

You don’t want watering to make the container go from being light to feeling like a brick of lead.

Soil for marijuana growing folklore says you’re supposed to water until the water runs out of the bottom of the container.

By the time that happens, in most cases, you’ve grossly overwatered.

There’s so much water in the root zone that oxygen and open space is gone.

There are reasons for watering so much that water flows out of the bottom of pots, and we’ll talk about them in our next article.

Just know that in general, if you’ve watered so much that water is running out of the bottom, it’s too much water.

This is how the same soil as in the main image looks when it’s properly watered—a lot darker. © Copyright, Gary Anderson, 2016

In overwatered, clumped-up soil, your roots can’t move around as they grow and search for nutrients and water, and they can’t get oxygen.

A wet root zone is a great environment for root rot.

One tool that many growers use to manage soil for marijuana growing is a soil moisture meter.

Most soil moisture meters don’t work every well.

The rule is, if a soil moisture meter costs less than $80, it probably won’t work well or last long.

However, you can get professional models such as these that do work well and have durability.

Please look at the photos accompanying this article that give you examples of what quality soil looks like when it’s properly watered.

Come back for our next article in this series on working with soil for marijuana growing.